1. Field of the Invention:
The invention relates in general to handrails for transportation apparatus, such as escalators and moving walks, and more specifically to handrails which are extruded from an elastomeric material.
2. Description of the Prior Art:
Handrails for transportation apparatus may be built up of several plies of canvas and rubber, and molded into a composite body member, or they may be extruded using a suitable polymeric material. The extrusion process is attractive from an economic viewpoint, as long runs may be made. Desired lengths are simply cut from a longer length. Our U.S. Pat. No. 4,618,387 sets forth methods of splicing the ends of such a handrail into a continuous loop.
Selection of the resulting hardness of the elastomeric material used in the extrusion of handrails is a compromise between lateral stiffness and longitudinal flexibility. The handrail must have sufficient longitudinal flexibility to enable it to follow a handrail guide around the turnarounds at the ends of an escalator or moving walk. On the other hand, it must be sufficiently stiff to provide reliable hand support for passengers on the transportation apparatus, and sufficiently stiff, at least laterally, to resist both accidental and deliberate derailment of the handrail from a handrail guide.
Other factors in the selection of the hardness of the elastomeric material relate to its coefficient of friction, as a series of driven and pressure rollers disposed on opposite sides of the handrail are often used to propel the handrail about a substantially closed guide loop. U.S. Pat. No. 3,712,447 discloses a push-pull closed guide loop arrangement, while suitable handrail drive arrangements are disclosed in U.S. Pat. Nos. 3,414,109 and 3,779,360, all of which are assigned to the same assignee as the present application. Thus, softer and more flexible material is desirable from the viewpoint of the driving function. Softer and more flexible material, however, wears more quickly than higher durometer material, and thus some means must be employed to prevent premature wear of the handrail body material.
Thus, it would be desirable, and it is the object of this invention, to provide an extruded handrail which is: (1) sufficiently flexible to smoothly traverse a handrail guide in the turnarounds of transportation apparatus, without any tendency to kink or otherwise resist such movement, (2) sufficiently stiff to function as a hand support for passengers, (3) sufficiently stiff in lateral stiffness to resist derailment of the handrail from a handrail guide, (4) sufficiently soft to provide the coefficient of friction required for driven and pressure rollers to propel the handrail about a handrail guide without slippage between the driven rollers and the handrail, and (5) sufficiently hard to provide an acceptable rate of wear.